EP0153785B1 - Process for producing tubular bodies and device for carrying out the process - Google Patents

Process for producing tubular bodies and device for carrying out the process Download PDF

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Publication number
EP0153785B1
EP0153785B1 EP85200214A EP85200214A EP0153785B1 EP 0153785 B1 EP0153785 B1 EP 0153785B1 EP 85200214 A EP85200214 A EP 85200214A EP 85200214 A EP85200214 A EP 85200214A EP 0153785 B1 EP0153785 B1 EP 0153785B1
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EP
European Patent Office
Prior art keywords
tubular mould
solid phase
mould
binder
tubular
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired
Application number
EP85200214A
Other languages
German (de)
French (fr)
Other versions
EP0153785A3 (en
EP0153785A2 (en
Inventor
Hans Dr. Lydtin
Rolf Dr. Rer. Nat. Clasen
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Philips Intellectual Property and Standards GmbH
Koninklijke Philips NV
Original Assignee
Philips Patentverwaltung GmbH
Philips Gloeilampenfabrieken NV
Koninklijke Philips Electronics NV
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Publication date
Application filed by Philips Patentverwaltung GmbH, Philips Gloeilampenfabrieken NV, Koninklijke Philips Electronics NV filed Critical Philips Patentverwaltung GmbH
Publication of EP0153785A2 publication Critical patent/EP0153785A2/en
Publication of EP0153785A3 publication Critical patent/EP0153785A3/en
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Publication of EP0153785B1 publication Critical patent/EP0153785B1/en
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    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
    • C03B19/00—Other methods of shaping glass
    • C03B19/06—Other methods of shaping glass by sintering, e.g. by cold isostatic pressing of powders and subsequent sintering, by hot pressing of powders, by sintering slurries or dispersions not undergoing a liquid phase reaction
    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
    • C03B19/00—Other methods of shaping glass
    • C03B19/04—Other methods of shaping glass by centrifuging
    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
    • C03B37/00—Manufacture or treatment of flakes, fibres, or filaments from softened glass, minerals, or slags
    • C03B37/01—Manufacture of glass fibres or filaments
    • C03B37/012—Manufacture of preforms for drawing fibres or filaments
    • C03B37/0128—Manufacture of preforms for drawing fibres or filaments starting from pulverulent glass
    • C03B37/01285—Manufacture of preforms for drawing fibres or filaments starting from pulverulent glass by centrifuging
    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
    • C03B2201/00—Type of glass produced
    • C03B2201/06—Doped silica-based glasses
    • C03B2201/30—Doped silica-based glasses doped with metals, e.g. Ga, Sn, Sb, Pb or Bi
    • C03B2201/31—Doped silica-based glasses doped with metals, e.g. Ga, Sn, Sb, Pb or Bi doped with germanium
    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
    • C03B2201/00—Type of glass produced
    • C03B2201/06—Doped silica-based glasses
    • C03B2201/30—Doped silica-based glasses doped with metals, e.g. Ga, Sn, Sb, Pb or Bi
    • C03B2201/32—Doped silica-based glasses doped with metals, e.g. Ga, Sn, Sb, Pb or Bi doped with aluminium

Definitions

  • the invention relates to a method for producing tubular bodies, in which a mixture of the material of the body to be formed in powder form (solid phase) with a binder in the liquid phase is introduced into a hollow mold with a geometry corresponding to the geometry of the body to be formed, such that that the hollow mold is rotated about its longitudinal axis, the powder-binder mixture being deposited on the inner wall of the hollow mold and excess binder being removed, after which the resulting green body is processed further.
  • the invention further relates to a device for performing such a method.
  • a method of the type described in the opening paragraph is known from GB-A-682 580. This known method is used to remove porous glass tubes, e.g. B. as a filter for laboratory purposes, where it depends on a uniform pore distribution and pore size between the melted glass particles and the pores must be interconnected.
  • suspensions of glass powder of as uniform a grain size as possible in a binder that prevents the solid particles from settling e.g. B. an aqueous glycerol solution, with the addition of wetting agents and agents that prevent foaming of the suspension, constantly stirred to keep the solid particles within the suspension in a desired, corresponding to the later porosity, distribution state before they are introduced into the centrifuge and form a loose bond of separated solid particles on the inner wall.
  • Such a method is not suitable if solid particles are to be separated on a centrifuge inner wall, which must be present in the densest possible solid packing.
  • a process for the production of glass bodies, which is to be used as a so-called preform for the production of optical fibers, which also works with the centrifugal separation of glass particles, but not in a suspension, but dry, on the inner wall of a centrifuge is known from DE- C-3 240 355.
  • the solid particles are kept dry as a bulk body during centrifugal centrifugal force on the inner surface of a support body.
  • the bulk of the bulk body must then be stabilized in shape by means of heating and / or by applying hardening adhesives.
  • the dimensionally stabilized bulk material must then be pressed into a fine-pored solid, since the density of the solid particles achieved by the bed is not sufficient for the requirements that have to be placed on a preform for optical fibers.
  • the disadvantages associated with this known method are that firstly the shape of the bulk material has to be stabilized, but that the density of the solid body packing required for a preform for optical fibers also has to be produced by a subsequent pressing process.
  • the subsequent pressing process for the formation of a fine-pored solid has the disadvantage, in addition to being an additional process step, that a defined inhomogeneous refractive index distribution initially produced by the jetting of grains of different substances could be impaired.
  • the invention has for its object to improve the above-mentioned method in such a way that tubular bodies can be produced which have a very high packing density of the solid particles in the deposited layer, with which layers of solid particles of different chemical composition are defined and are deposited in a high packing density can, without the defined arrangement of chemically different solid particle layers being disturbed by subsequent processing steps of the green body and which makes it possible, in particular, to produce SiO 2 tubes of high density, homogeneity and purity, which just have such a low porosity that subsequent cleaning is influenced of gases can be carried out well and sintering to quartz glass tubes, in particular of a quality required for the production of optical waveguides, is made possible.
  • the binder and the solid phase are introduced into the hollow mold one after the other via metering devices, the liquid phase first being deposited on the inner wall of the hollow mold.
  • binders can first be deposited in the form of a liquid film on the inner wall of the hollow mold.
  • the binder can comprise liquids of different types. Any indifferent liquid can be used for this purpose, e.g. As water, organic liquids, optionally with the addition of dispersants, stabilizers or the like, which are well known to those skilled in the art.
  • the powdery solid phase can then be deposited on the binder layer.
  • Solid particles are driven onto the liquid film, where wetting can take place and the fine particles are coated with dispersant and are prevented from premature coagulation.
  • the solid particles drift separately from one another to the inner wall of the hollow mold, where they are deposited with a high packing density (50 to 90% of the theoretically possible packing density).
  • the gaps remain filled with the liquid phase, which can contain a dispersant and a binder.
  • the powder can be introduced continuously in the axial direction.
  • the addition of the liquid phase can also be carried out continuously via separate feeders and can be dimensioned such that the deposited solid particle layer is always only covered with a thin film of liquid.
  • the advantages here are that the process time can be considerably reduced compared to a single addition of the required amount of liquid phase, since the deposition time is proportional to the viscosity of the liquid phase and the film thickness. This measure minimizes the separation of solid particles of different densities and dimensions.
  • the hollow mold to be coated on the inside can be rotatable about its longitudinal axis both in the horizontal and in the vertical position.
  • the binder and the solid phase are introduced into the hollow mold simultaneously via the metering devices, excess liquid phase being sucked off during the process.
  • Such classification can be carried out, for example, by mixing 1200 g of a commercially available starting material for the production of optical waveguides (highly disperse Si0 2 -P U l V er) in 2000 cm 3 aqueous concentrated ammonia solution and dispersing them under the influence of ultrasound for 30 minutes. Such a suspension is centrifuged in a large laboratory centrifuge at 2.2 ⁇ 10 4 g for 30 min, the clear solution is poured off and the sedimented bodies are dried at 120 ° C. for one hour. Subsequently, the classification into fine, medium and coarse powder takes place in that the sediment body is divided into three parts according to the separated grain fractions. Each third of the original sediment body can now be successfully used alone as a starting material for producing a green body by the method according to the invention.
  • a sliding film is applied to the inner wall of the hollow mold prior to the application of powder and binder to make it easier to demould the green body.
  • the sliding film can preferably be made of high molecular weight hydrocarbons, e.g. B. Paraffin exist.
  • a paraffin with a melting point of 46 to 50 ° C is used; the green body sedimented on the inner wall of the hollow mold can then be heated by gently heating the hollow mold with z. B. a hot air blower or z. B. can be easily removed from the mold by immersion in hot water.
  • single- or multi-phase liquid-binder mixtures are used as binders, inorganic / organic solutions, organic substances or else a hydrophobic liquid being preferably used as binders.
  • a hydrophobic liquid is, for example, a paraffin liquid at room temperature.
  • solid particle transport takes place in the binder. It is believed that the on the surface of e.g. B. Si0 2 solid particles adsorbed OH groups play a role here that z. B. sufficient stability of the solid particles with one another is achieved by bridging.
  • demolding can easily be achieved by heating the hollow mold to around 100 to 150 ° C.
  • UV-curing polymers which are thin at room temperature are practical for an industrial production process.
  • the solid phase is a material suitable for optical waveguides, in particular highly disperse SiO 2 powder with a grain size in the range from 5 to 500 nm, preferably from 10 to 200 nm, without or with suitable for setting a desired refractive index ( r) doping.
  • the doping can for example be about Ge0 2 powder is added.
  • the powder ceramic material, for. B. for the production of optical waveguides introduced in batches of different chemical composition in succession in the hollow mold, in particular such that layers of different compositions according to a desired refractive index profile deposit on the inner wall of the hollow mold.
  • the production of the solid phase is carried out via a chemical process in the gas phase immediately before its deposition on the inner wall of the hollow mold, in such a way that gaseous starting substances are heated and reactive in or immediately before the hollow mold acting as a centrifuge are implemented, the gas phase acting as a dispersant for the resulting solid phase.
  • SiH 4 and 0 2 are advantageously used as gaseous starting substances; however, the skilled worker is familiar with such processes for B. also known the halides of silicon.
  • the solid particles that arise during the process flow directly into the acceleration field of the centrifuge and sediment on the inner wall of the hollow mold.
  • An advantage of this "in situ" process is the exact meterability of the solid particles and their almost ideal dispersion in the gas phase. The disadvantage of a convective gas flow can be compensated for in this way.
  • a device for carrying out the method according to the invention with a hollow mold drivable as a centrifuge, on the inner wall of which substances introduced into the hollow mold can be separated by centrifugal forces is characterized according to the invention in that the hollow mold can be closed by two aperture diaphragms arranged perpendicular to the longitudinal axis of the hollow mold, through the openings of which at least one tube each can be displaced as a metering device along the longitudinal axis of the hollow mold, such that part of the tube (s) remains outside the hollow mold and from there can be loaded with substances to be introduced into the interior of the hollow mold and the other, in the interior located part of the tube (s) is provided with at least one outlet opening (nozzle) through which substances in the tubes first enter the interior of the hollow mold and can be deposited on the inner wall thereof, the hollow mold according to advantageous developments of the invention an R ear is closed at the end with the aperture diaphragm, the centrifugal drive of the hollow mold is carried out with the aid of a motor,
  • the figure shows a schematic representation of a centrifuge arrangement with a hollow mold for the production of tubular bodies according to the invention.
  • a liquid phase 17 is first introduced and by centrifugation evenly in the form of a liquid film 13 on the Distributed inner wall 11 of the tube used as a hollow mold 1.
  • a metering device movable in the axial and radial direction in the form of at least one tube 7 with outlet openings 9 feeds powdery starting material 15 to the interior of the tube acting as a hollow mold 1.
  • the solid particles are driven onto the liquid film 13 by centrifugal forces, where wetting can take place and the fine particles are coated with dispersant and are prevented from premature coagulation.
  • the solid particles drift separately from one another in the direction of the inner wall 11 of the hollow mold 1, where they are deposited with a high packing density (50 to 90% of the theoretically possible packing density).
  • the z. B. contains dispersant and a binder.
  • the solid particle input can be continuously shifted in the axial direction.
  • the addition of the liquid phase 17 can also be carried out continuously via a separate metering device in the form of a further tube 7 'via a nozzle 99 and can be dimensioned such that the deposited solid particle layer is always covered only with a thin film of liquid is.
  • a rotating high-strength metal tube e.g. B. made of steel or aluminum, with a total length of 160 mm and an outer diameter of 60 mm, the end faces of which are provided with removable aperture diaphragms in a thickness of 5 mm, at a rotation frequency of initially 1000 rpm, about 120 ml of a 15th % polyvinyl alcohol solution (degree of polymerization 350) introduced.
  • 210 g of finely divided, highly disperse SiO 2 powder with a metering rate of 1 g / min is also uniformly moved by moving the metering device back and forth at a speed of 5 m / using a metering device which is movable in the axial direction. min while increasing the rotation frequency of the pipe to 30,000 rpm.
  • the excess liquid film lying above the separator is suctioned off and the separated green body by slightly heating the substrate tube, for example to 50 to 100 ° C. demolded.
  • a thin layer deposition of a sliding film is recommended at the beginning of the process on the inner wall of the pipe, e.g. B. from paraffin.
  • the green body obtained in this way is characterized by great geometric accuracy and an almost location-independent density. The latter and the fact that after drying at 120 ° C and expulsion of the binder by slow heating to 500 ° C at a heating rate of 150 ° C / h, a small open pore structure is available, a subsequent chlorine cleaning of the green body and sintering possible with quartz glass tubes.
  • Such impurities were removed at 800 ° C in a saturated at room temperature with SOCI 2 0 2 flow at a flow rate of 1 to 2 I / min.
  • the impurities are chlorinated and escape as a volatile phase.
  • the sintering of the slightly open-pore green body to transparent, bubble-free glass was carried out at 1500 ° C with a lowering speed of 3 mm / min under a helium / chlorine (1 to 3%) atmosphere of a pressure of 10 5 Pa and a flow rate of 1 1 / min.
  • a high-purity, transparent quartz glass tube with a high surface area was obtained by this process.
  • An accelerated production of green bodies based on SiO 2 / binder can be achieved in such a way that the liquid phase (see Example 1) is also continuously fed during the addition of solid particles, such that only a thin film of liquid (1 mm, preferably 10 up to 100 ⁇ m) above the already separated solid particles.
  • This measure makes it possible, on the one hand, to increase the speed of adding solid particles to 5 g / min without problems and, furthermore, to reduce segregation of different sizes of solid particles during the short sedimentation time.
  • liquid phase as described in Example 1, is introduced into the mold.
  • starting powder solid particles
  • varying their relationship to each other over time almost any composition can be built up over the wall thickness.
  • the defined change in the refractive index over the radius is of great importance for the production of optical waveguides.
  • z. B. a second metering device in the form of a second tube, which can also be moved in the axial direction
  • z. B. 15 wt .-% Ge0 2 containing Si0 2 powder can be introduced into the interior of the rotating hollow mold simultaneously with pure Si0 2 powder.
  • pure SiO 2 powder is fed in at a dosage rate of 1 g / min.
  • the metering rate of the pure Si0 2 powder is then linearly reduced to zero while the metering rate is kept constant at 1 g / min, with a simultaneous and corresponding increase in the metering rate of the Si0 2 -Ge0 2 powder stream.
  • gradient index fibers with attenuation of less than 1 dB / km at 1300 nm can be produced in this way.
  • tubular bodies based on solid particles in which the finely powdered starting material is centrifuged into a hydrophobic liquid, can be carried out in the following way.
  • demolding from the hollow mold can be carried out by heating the hollow mold to about 100 to 150 ° C.
  • thermoplastic or thermosetting plastics instead of a hydrophobic liquid as the binder, it is also advantageous to use thermoplastic or thermosetting plastics as the dispersion matrix and binder. It has proven to be interesting to use UV-curing lacquers which are thin at room temperature and only harden when exposed to UV radiation.
  • the result is that the solid particles formed immediately behind the burner nozzles get directly into the acceleration field of the centrifuge and sediment in the direction of the inner wall of the hollow mold.
  • An advantage of this in situ process is the precise meterability of the materials and their almost ideal dispersion in the gas phase.
  • pipes can also be produced from any other materials, e.g. B. made of aluminum oxide or iron.
  • Highly pure and dimensionally accurate quartz tubes as can be produced by the present method, can be used in the production of optical waveguides, but also in the production of halogen and gas discharge lamps.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Materials Engineering (AREA)
  • Organic Chemistry (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • General Life Sciences & Earth Sciences (AREA)
  • Geochemistry & Mineralogy (AREA)
  • Dispersion Chemistry (AREA)
  • Manufacturing Of Tubular Articles Or Embedded Moulded Articles (AREA)
  • Glass Melting And Manufacturing (AREA)
  • Manufacture, Treatment Of Glass Fibers (AREA)

Abstract

1. A method of manufacturing tubes, in which a mixture of the tube material in powder form (solid phase 15) and a binder in a liquid phase (17) is introduced into a tubular mould (1) having a geometry which corresponds to the geometry of the tube to be formed, in such manner that the tubular mould is rotated about its longitudinal axis, the powder-binder mixture depositing on the inner wall (11) of the tubular mould and excessive binder being removed after which the green body formed is processed further, characterized in that the solid phase (15) and the liquid phase (17) are introduced separately into the tubular mould (1).

Description

Die Erfindung betrifft ein Verfahren zur Herstellung von rohrförmigen Körpern, bei welchem ein Gemisch aus dem Werkstoff des auszubildenden Körpers in Pulverform (feste Phase) mit einem Bindemittel in flüssiger Phase in eine Hohlform mit einer der Geometrie des auszubildenden Körpers entsprechenden Geometrie eingebracht wird, derart, daß die Hohlform um ihre Längsachse gedreht wird, wobei sich das Pulver-Bindemittel-Gemisch an der Innenwandung der Hohlform ablagert und überschüssiges Bindemittel entfernt wird, wonach der entstandene Grünkörper weiterbearbeitet wird.The invention relates to a method for producing tubular bodies, in which a mixture of the material of the body to be formed in powder form (solid phase) with a binder in the liquid phase is introduced into a hollow mold with a geometry corresponding to the geometry of the body to be formed, such that that the hollow mold is rotated about its longitudinal axis, the powder-binder mixture being deposited on the inner wall of the hollow mold and excess binder being removed, after which the resulting green body is processed further.

Die Erfindung betrifft weiter eine Vorrichtung zur Durchführung eines solchen Verfahrens.The invention further relates to a device for performing such a method.

Ein Verfahren der eingangs beschriebenen Art ist bekannt aus GB-A-682 580. Dieses bekannte Verfahren dient dazu, poröse Glasrohre, z. B. als Filter für Laborzwecke, herzustellen, wobei es auf eine möglichst gleichmäßige Porenverteilung und Porengröße zwischen den angeschmolzenen Glaspartikeln ankommt und die Poren untereinander in Verbindung stehen müssen.A method of the type described in the opening paragraph is known from GB-A-682 580. This known method is used to remove porous glass tubes, e.g. B. as a filter for laboratory purposes, where it depends on a uniform pore distribution and pore size between the melted glass particles and the pores must be interconnected.

Zu diesem Zweck werden Suspensionen von Glaspulver möglichst einheitlicher Korngröße in einem, ein Absetzen der Feststoffpartikel verhindernden Bindemittel, z. B. einer wässerigen Glyzerinlösung, unter Zusatz von Benetzungsmitteln und Mitteln, die ein Aufschäumen der Suspension verhindern, ständig gerührt, um die Feststoffpartikel innerhalb der Suspension in einem gewünschten, der späteren Porosität entsprechenden, Verteilungszustand zu halten, bevor sie in die Zentrifuge eingebracht werden und dort auf der Innenwand einen lockeren Verbund abgeschiedener Feststoffpartikel bilden.For this purpose, suspensions of glass powder of as uniform a grain size as possible in a binder that prevents the solid particles from settling, e.g. B. an aqueous glycerol solution, with the addition of wetting agents and agents that prevent foaming of the suspension, constantly stirred to keep the solid particles within the suspension in a desired, corresponding to the later porosity, distribution state before they are introduced into the centrifuge and form a loose bond of separated solid particles on the inner wall.

Ein solches Verfahren ist nicht geeignet, wenn auf einer Zentrifugeninnenwand Feststoffpartikel abgeschieden werden sollen, die in möglichst dichter Feststoffpackung vorliegen müssen.Such a method is not suitable if solid particles are to be separated on a centrifuge inner wall, which must be present in the densest possible solid packing.

Ein Verfahren zur Herstellung von Glaskörpern, die als sogenannte Preform für die Herstellung von optischen Fasern verwendet werden sollen, das ebenfalls mit der zentrifugalen Abscheidung von Glaspartikeln, jedoch nicht in einer Suspension, sondern trocken, auf der Innenwand einer Zentrifuge arbeitet, ist aus DE-C-3 240 355 bekannt. Hier werden die Feststoffpartikel trocken als Schüttkörper während der Schüttung durch Rotationsfliehkraft an der Innenfläche eines Stötzkörpers gehalten. Der Schüttkörper muß anschließend an seinem Umfang formstabilisiert werden mittels Erhitzen und/oder durch Auftragen von erhärtenden Klebern. Der formstabilisierte Schüttkörper muß dann anschließend zu einem feinporigen Festkörper verpreßt werden, da die durch die Schüttung erreichte Dichte der Feststoffpartikel für die Anfurderungen, die an eine Preform für optische Fasern gestellt werden müssen, nicht ausreicht. Mit diesem bekannten Verfahren sind die Nachteile verbunden, daß erstens eine Formstabilisierung der Schüttkörper vorgenommen werden muß, daß aber auch die für eine Preform für optische Fasern erforderliche Dichte der Festkörperpackung durch einen anschließenden Preßprozeß erst noch hergestellt werden muß. Der anschließende Preßprozeß zur Bildung eines feinporigen Festkörpers hat außer, daß er einen zusätzlichen Prozeßschritt darstellt, noch den Nachteil, daß eine durch die Schöttung von Körnern unterschiedlicher Stoffe zunächst hergestellte definierte inhomogene Brechungsindexverteilung beeinträchtigt werden könnte.A process for the production of glass bodies, which is to be used as a so-called preform for the production of optical fibers, which also works with the centrifugal separation of glass particles, but not in a suspension, but dry, on the inner wall of a centrifuge is known from DE- C-3 240 355. Here, the solid particles are kept dry as a bulk body during centrifugal centrifugal force on the inner surface of a support body. The bulk of the bulk body must then be stabilized in shape by means of heating and / or by applying hardening adhesives. The dimensionally stabilized bulk material must then be pressed into a fine-pored solid, since the density of the solid particles achieved by the bed is not sufficient for the requirements that have to be placed on a preform for optical fibers. The disadvantages associated with this known method are that firstly the shape of the bulk material has to be stabilized, but that the density of the solid body packing required for a preform for optical fibers also has to be produced by a subsequent pressing process. The subsequent pressing process for the formation of a fine-pored solid has the disadvantage, in addition to being an additional process step, that a defined inhomogeneous refractive index distribution initially produced by the jetting of grains of different substances could be impaired.

Dadurch, daß die Pulver trocken zentrifugiert werden, können auch Probleme hinsichtlich der Homogenität des abgeschiedenen Materials auftreten; aufgrund elektrostatischer Aufladungen wird eine gleichmäßige Sedimentation und der Zusammenhalt der Formkörper erschwert. Ein weiterer Nachteil ist, daß der Schüttkörper ein örtlich unterschiedliches Schwindungsverhalten aufweisen kann; dies führt leicht zu Delamination einzelner Schichten.By centrifuging the powders dry, problems with the homogeneity of the deposited material can also arise; Due to electrostatic charges, uniform sedimentation and the cohesion of the shaped bodies are made more difficult. Another disadvantage is that the bulk body can have a different local shrinkage behavior; this easily leads to delamination of individual layers.

Der Erfindung liegt die Aufgabe zugrunde, das eingangs genannte Verfahren derart zu verbessern, daß rohrförmige Körper hergestellt werden können, die eine sehr hohe Packungsdichte der Feststoffpartikel in der abgeschiedenen Schicht aufweisen, mit dem Schichten von Feststoffpartikeln unterschiedlicher chemischer Zusammensetzung definiert und in hoher Packungsdichte abgeschieden werden können, ohne daß die definierte Anordnung chemisch unterschiedlicher Feststoffpartikelschichten durch nachfolgende Bearbeitungsschritte des Grünkörpers gestört wird und das es ermöglicht, insbesondere Si02-Rohre hoher Dichte, Homogenität und Reinheit herzustellen, die gerade noch eine so geringe Porosität aufweisen, daß eine nachfolgende Reinigung unter Einfluß von Gasen gut durchführbar ist und eine Sinterung zu Quarzglasrohren insbesondere einer für die Herstellung von optischen Wellenleitern erforderlichen Qualität ermöglicht wird.The invention has for its object to improve the above-mentioned method in such a way that tubular bodies can be produced which have a very high packing density of the solid particles in the deposited layer, with which layers of solid particles of different chemical composition are defined and are deposited in a high packing density can, without the defined arrangement of chemically different solid particle layers being disturbed by subsequent processing steps of the green body and which makes it possible, in particular, to produce SiO 2 tubes of high density, homogeneity and purity, which just have such a low porosity that subsequent cleaning is influenced of gases can be carried out well and sintering to quartz glass tubes, in particular of a quality required for the production of optical waveguides, is made possible.

Diese Aufgabe wird erfindungsgemäß dadurch gelöst, daß die feste Phase und die flüssige Phase getrennt voneinander in die Hohlform eingebracht werden.This object is achieved in that the solid phase and the liquid phase are introduced into the hollow mold separately from one another.

Nach einer vorteilhaften Weiterbildung der Erfindung werden das Bindemittel und die feste Phase nacheinander über Dosiervorrichtungen in die Hohlform eingebracht, wobei zunächst die flüssige Phase auf der Innenwandung der Hohlform abgeschieden wird.According to an advantageous development of the invention, the binder and the solid phase are introduced into the hollow mold one after the other via metering devices, the liquid phase first being deposited on the inner wall of the hollow mold.

Hiermit ist der Vorteil verbunden, daß zunächst Bindemittel in Form eines Flüssigkeitsfilmes auf der Innenwandung der Hohlform abgeschieden werden kann.This has the advantage that binders can first be deposited in the form of a liquid film on the inner wall of the hollow mold.

Das Bindemittel kann Flüssigkeiten unterschiedlicher Art umfassen. Für diesen Zweck kann jede indifferente Flüssigkeit benutzt werden, z. B. Wasser, organische Flüssigkeiten, gegebenenfalls unter Zusatz von Dispergierstoffen, Stabilisierungsstoffen oder dergleichen, die dem Fachmann wohl bekannt sind.The binder can comprise liquids of different types. Any indifferent liquid can be used for this purpose, e.g. As water, organic liquids, optionally with the addition of dispersants, stabilizers or the like, which are well known to those skilled in the art.

Anschließend kann die pulverförmige feste Phase auf der Bindemittelschicht abgeschieden werden. Durch Zentrifugalkräfte werden die Feststoffpartikel auf den Flüssigkeitsfilm getrieben, wo eine Benetzung erfolgen kann und die feinen Teilchen mit Dispergiermittel überzogen und vor einer frühzeitigen Koagulation bewahrt werden. Im Flüssigkeitsfilm driften die Feststoffpartikel nun getrennt voneinander zur Innenwandung der Hohlform, wo sie mit großer Packungsdichte (50 bis 90 % der theoretisch möglichen Packungsdichte) abgelagert werden. Die Zwischenräume bleiben mit der flüssigen Phase, die ein Dispergiermittel und ein Bindemittel enthalten kann, ausgefüllt. Um eine gleichmäßige Ablagerung der Feststoffpartikel längs der Achse der Hohlform zu erleichtern, kann die Pulvereingabe kontinuierlich in axialer Richtung verschiebbar vorgenommen werden. Um eine möglichst schnelle Abscheidung zu erreichen, kann die Zugabe der flüssigen Phase ebenfalls kontinuierlich über getrennte Zuführungen vorgenommen und gerade so bemessen werden, daß die abgeschiedene Feststoffpartikelschicht stets nur mit einem dünnen Flössigkeitsfilm bedeckt ist. Die Vorteile sind hierbei, daß die Prozeßdauer gegenüber einer einmaligen Zugabe der benötigten Menge an flüssiger Phase erheblich vermindert werden kann, da die Abscheidungszeit proportional zur Viskosität der flössigen Phase und der Filmdicke ist. Eine Separation von Feststoffpartikeln unterschiedlicher Dichte und Abmessungen wird durch diese Maßnahme minimiert. Die innen zu beschichtende Hohlform kann sowohl in horizontaler als auch in vertikaler Position um ihre Längsachse drehbar sein.The powdery solid phase can then be deposited on the binder layer. By centrifugal forces Solid particles are driven onto the liquid film, where wetting can take place and the fine particles are coated with dispersant and are prevented from premature coagulation. In the liquid film, the solid particles drift separately from one another to the inner wall of the hollow mold, where they are deposited with a high packing density (50 to 90% of the theoretically possible packing density). The gaps remain filled with the liquid phase, which can contain a dispersant and a binder. In order to facilitate a uniform deposition of the solid particles along the axis of the hollow mold, the powder can be introduced continuously in the axial direction. In order to achieve the fastest possible separation, the addition of the liquid phase can also be carried out continuously via separate feeders and can be dimensioned such that the deposited solid particle layer is always only covered with a thin film of liquid. The advantages here are that the process time can be considerably reduced compared to a single addition of the required amount of liquid phase, since the deposition time is proportional to the viscosity of the liquid phase and the film thickness. This measure minimizes the separation of solid particles of different densities and dimensions. The hollow mold to be coated on the inside can be rotatable about its longitudinal axis both in the horizontal and in the vertical position.

Nach einer weiteren vorteilhaften Ausgestaltung der Erfindung werden das Bindemittel und die feste Phase gleichzeitig über die Dosiervorrichtungen in die Hohlform eingebracht, wobei überschüssige flüssige Phase während des Prozesses abgesaugt wird.According to a further advantageous embodiment of the invention, the binder and the solid phase are introduced into the hollow mold simultaneously via the metering devices, excess liquid phase being sucked off during the process.

Hiermit ist der Vorteil verbunden, daß jeweils nur ein sehr dünner Flüssigkeitsfilm (1 mm, vorzugsweise 10 bis 100 l1m) über bereits abgeschiedenen Feststoffpartikeln steht, was die Sedimentationszeit der Feststoffpartikel verkürzt und damit eine Entmischung von Feststoffpartikeln unterschiedlicher Größe während der Sedimentationszeit vermindert. Nach diesem Verfahren lassen sich alle irgendwie strukturierten Rohre (Vorformen für Singlemoden- und Gradientenfasern) herstellen.This has the advantage that in each case only a very thin liquid film (1 mm, preferably 10 to 100 l1m) stands over already deposited solid particles, which shortens the sedimentation time of the solid particles and thus reduces segregation of solid particles of different sizes during the sedimentation time. All somehow structured tubes (preforms for single-mode and gradient fibers) can be produced using this method.

In diesem Zusammenhang ist von Bedeutung, daß Grünkörper, die anschließend zu transparentem Glas gesintert werden sollen, eine sehr gleichmäßige Kornverteilung in axialer und radialer Richtung aufweisen müssen. Nur so lassen sich Schrumpfungsrisse beim Trocknen dieser aus submikroskopischen Teilchen bestehenden Grünkörper vermindern. Da fertig im Handel erhältliche bekannte Feststoffpartikel-Ausgangsmaterialien, die für die Herstellung von optischen Wellenleitern verwendet werden, breite Kornverteilungen aufzuweisen pflegen (z. B. Korndurchmesser von 5 bis 500 nm), ist es notwendig, zunächst eine Klassierung der Ausgangspulver vorzunehmen. Eine solche Klassierung kann beispielsweise so erfolgen, daß 1200 g eines im Handel erhältlichen Ausgangsmaterials für die Herstellung von optischen Wellenleitern (hochdisperses Si02-PUlVer) in 2000 cm3 wässeriger konzentrierter Ammoniaklösung verrührt und 30 Minuten lang unter Ultraschalleinwirkung dispergiert werden. Eine solche Suspension wird in einer großen Laborzentrifuge 30 min bei 2,2 x 104 g zentrifugiert, die klare Lösung abgegossen und die sedimentierten Körper eine Stunde bei 120°C getrocknet. Anschließend erfolgt die Klassierung in feines, mittleres und grobes Pulver, dadurch, daß der Sedimentkörper entsprechend den abgeschiedenen Kornfraktionen in drei Teile aufgeteilt wird. Jedes Drittel des ursprünglichen Sedimentkörpers kann jetzt allein als Ausgangsmaterial zur Herstellung eines Grünkörpers nach dem Verfahren gemäß der Erfindung erfolgreich eingesetzt werden.In this context, it is important that green bodies that are subsequently to be sintered into transparent glass must have a very uniform grain distribution in the axial and radial directions. This is the only way to reduce shrinkage cracks when drying these green bodies consisting of submicroscopic particles. Since commercially available known solid particle starting materials which are used for the production of optical waveguides tend to have broad particle distributions (e.g. particle diameters from 5 to 500 nm), it is necessary to first classify the starting powders. Such classification can be carried out, for example, by mixing 1200 g of a commercially available starting material for the production of optical waveguides (highly disperse Si0 2 -P U l V er) in 2000 cm 3 aqueous concentrated ammonia solution and dispersing them under the influence of ultrasound for 30 minutes. Such a suspension is centrifuged in a large laboratory centrifuge at 2.2 × 10 4 g for 30 min, the clear solution is poured off and the sedimented bodies are dried at 120 ° C. for one hour. Subsequently, the classification into fine, medium and coarse powder takes place in that the sediment body is divided into three parts according to the separated grain fractions. Each third of the original sediment body can now be successfully used alone as a starting material for producing a green body by the method according to the invention.

Nach einer vorteilhaften Weiterbildung des Verfahrens nach der Erfindung wird auf die Innenwandung der Hohlform vor Anbringen von Pulver und Bindemittel ein Gleitfilm zur besseren Entformbarkeit des Grünkörpers aufgebracht. Der Gleitfilm kann vorzugsweise aus hochmolekularen Kohlenwasserstoffen, z. B. Paraffin bestehen. Beispielsweise wird ein Paraffin mit einem Schmelzpunkt von 46 bis 50°C eingesetzt; der auf der Innenwandung der Hohlform sedimentierte Grönkörper kann dann durch leichtes Erwärmen der Hohlform mit z. B. einem Heißluftgebläse oder z. B. durch Eintauchen in heißes Wasser sehr leicht entformt werden.According to an advantageous development of the method according to the invention, a sliding film is applied to the inner wall of the hollow mold prior to the application of powder and binder to make it easier to demould the green body. The sliding film can preferably be made of high molecular weight hydrocarbons, e.g. B. Paraffin exist. For example, a paraffin with a melting point of 46 to 50 ° C is used; the green body sedimented on the inner wall of the hollow mold can then be heated by gently heating the hollow mold with z. B. a hot air blower or z. B. can be easily removed from the mold by immersion in hot water.

Nach vorteilhaften Weiterbildungen der Erfindung werden als Bindemittel ein- oder mehrphasige Flüssigkeits-Binder-Gemische eingesetzt, wobei als Bindemittel vorzugsweise anorganisch/organische Lösungen, organische Substanzen oder auch eine hydrophobe Flüssigkeit eingesetzt wird.According to advantageous developments of the invention, single- or multi-phase liquid-binder mixtures are used as binders, inorganic / organic solutions, organic substances or else a hydrophobic liquid being preferably used as binders.

Eine hydrophobe Flüssigkeit ist beispielsweise ein bei Raumtemperatur flüssiges Paraffin. Wider Erwarten findet auch hier ein Feststoffpartikeltransport im Bindemittel statt. Es wird vermutet, daß die auf der Oberfläche von z. B. Si02-Feststoffpartikeln adsorbierten OH-Gruppen hier eine Rolle spielen, daß z. B. eine ausreichende Stabilität der Feststoffpartikel untereinander durch Brückenbildung erreicht wird.A hydrophobic liquid is, for example, a paraffin liquid at room temperature. Against all expectations, solid particle transport takes place in the binder. It is believed that the on the surface of e.g. B. Si0 2 solid particles adsorbed OH groups play a role here that z. B. sufficient stability of the solid particles with one another is achieved by bridging.

Nach der Sedimentation der Feststoffpartikel kann eine Entformung leicht durch Erwärmen der Hohlform auf etwa 100 bis 150°C erreicht werden.After sedimentation of the solid particles, demolding can easily be achieved by heating the hollow mold to around 100 to 150 ° C.

Praktisch für einen industriellen Fertigungsprozeß sind nach einer vorteilhaften Weiterbildung des Verfahrens gemäß der Erfindung als Bindemittel UV-härtende Polymere, die bei Raumtemperatur dünnflüssig sind.According to an advantageous development of the method according to the invention, UV-curing polymers which are thin at room temperature are practical for an industrial production process.

Nach weiteren vorteilhaften Ausgestaltungen der Erfindung ist die feste Phase ein für optische Wellenleiter geeigneter Werkstoff, insbesondere hochdisperses Si02-Pulver einer Korngröße im Bereich von 5 bis 500 nm, vorzugsweise von 10 bis 200 nm ohne oder mit für die Einstellung eines gewünschten Brechungsindex geeignete(r) Dotierung. Die Dotierung kann beispielsweise über Zugabe von Ge02-Pulver erfolgen.According to further advantageous embodiments of the invention, the solid phase is a material suitable for optical waveguides, in particular highly disperse SiO 2 powder with a grain size in the range from 5 to 500 nm, preferably from 10 to 200 nm, without or with suitable for setting a desired refractive index ( r) doping. The doping can for example be about Ge0 2 powder is added.

Nach vorteilhaften Weiterbildungen der Erfindung wird der pulverkeramische Werkstoff, z. B. für die Herstellung von optischen Wellenleitern, in Chargen abweichender chemischer Zusammensetzung nacheinander in die Hohlform eingebracht, insbesondere derart, daß sich Schichten unterschiedlicher Zusammensetzung entsprechend einem gewünschten Brechungsindexprofil auf der Innenwandung der Hohlform abscheiden. Durch Zuführung unterschiedlich zusammengesetzter fester Phasen und Variation ihres Verhältnisses zueinander über die Zeit lassen sich nahezu beliebige Zusammensetzungen über die Wanddicke aufbauen. Für die Herstellung von optischen Wellenleitern ist die definierte Änderung des Brechungsindex über den Radius von großer Bedeutung.According to advantageous developments of the invention, the powder ceramic material, for. B. for the production of optical waveguides, introduced in batches of different chemical composition in succession in the hollow mold, in particular such that layers of different compositions according to a desired refractive index profile deposit on the inner wall of the hollow mold. By adding differently composed solid phases and varying their relationship to one another over time, almost any composition can be built up over the wall thickness. The defined change in the refractive index over the radius is of great importance for the production of optical waveguides.

Durch Einsetzen mehrerer Dosiervorrichtungen ist es möglich, unterschiedliche Feststoffpartikelströme in den Innenraum der Hohlform zu leiten, z. B. reines Si02-Pulver und mit Ge02 dotiertes Si02-Pulver, um so beliebige Brechungsindexprofile im abgeschiedenen Grünkörper aufzubauen.By using several metering devices, it is possible to conduct different solid particle flows into the interior of the hollow mold, e.g. B. pure Si0 2 powder and Ge0 2 doped Si0 2 powder so as to build up any refractive index profiles in the deposited green body.

Nach einer vorteilhaften Ausgestaltung des Verfahrens nach der Erfindung wird die Herstellung der festen Phase über einen chemischen Prozeß in der Gasphase unmittelbar vor ihrer Abscheidung auf der Innenwandung der Hohlform vorgenommen, derart, daß gasförmige Ausgangssubstanzen in oder unmittelbar vor der als Zentrifuge wirkenden Hohlform erhitzt und reaktiv umgesetzt werden, wobei die Gasphase als Dispergiermittel für die entstehende feste Phase wirkt. Hierbei werden als gasförmige Ausgangssubstanzen vorteilhafterweise SiH4 und 02 eingesetzt; dem Fachmann sind für derartige Prozesse jedoch z. B. auch die Halogenide des Siliciums bekannt. Die während des Prozeßablaufes erst entstehenden Feststoffpartikel geraten direkt in das Beschleunigungsfeld der Zentrifuge und sedimentieren auf der Innenwandung der Hohlform. Ein Vorteil dieses "in situ"-Prozesses ist die genaue Dosierbarkeit der Feststoffpartikel und ihre nahezu ideale Dispersion in der Gasphase. Der Nachteil einer konvektiven Gasströmung kann hierdurch kompensiert werden.According to an advantageous embodiment of the method according to the invention, the production of the solid phase is carried out via a chemical process in the gas phase immediately before its deposition on the inner wall of the hollow mold, in such a way that gaseous starting substances are heated and reactive in or immediately before the hollow mold acting as a centrifuge are implemented, the gas phase acting as a dispersant for the resulting solid phase. SiH 4 and 0 2 are advantageously used as gaseous starting substances; however, the skilled worker is familiar with such processes for B. also known the halides of silicon. The solid particles that arise during the process flow directly into the acceleration field of the centrifuge and sediment on the inner wall of the hollow mold. An advantage of this "in situ" process is the exact meterability of the solid particles and their almost ideal dispersion in the gas phase. The disadvantage of a convective gas flow can be compensated for in this way.

Eine Vorrichtung zur Durchföhrung des erfindungsgemäßen Verfahrens mit einer als Zentrifuge antreibbaren Hohlform, auf deren Innenwandung durch Zentrifugalkräfte in die Hohlform eingebrachte Stoffe abscheidbar sind, ist erfindungsgemäß dadurch gekennzeichnet, daß die Hohlform durch zwei senkrecht zur Längsachse der Hohlform angeordnete Aperturblenden verschließbar ist, durch deren Öffnungen mindestens je ein Rohr als Dosiervorrichtung entlang der Längsachse der Hohlform verschiebbar sind, derart, daß ein Teil des(der) Rohres (Rohre) außerhalb der Hohlform verbleibt und von dort mit in den Innenraum der Hohlform einzubringenden Stoffen beschickbar ist und der andere, im Innenraum befindliche Teil des(der) Rohres (Rohre) mit mindestens je einer Austrittsöffnung (Düse) versehen ist, durch die in den Rohren befindliche Stoffe zunächst in den Innenraum der Hohlform gelangen und auf deren Innenwandung abscheidbar sind, wobei nach vorteilhaften Weiterbildungen der Erfindung die Hohlform ein Rohr ist, das stirnseitig mit den Aperturblenden verschließbar der Zentrifugalantrieb der Hohlform mit Hilfe eines Motors, mit dessen Achse die Hohlform verbunden ist, erfolgt oder der Zentrifugalantrieb der Hohlform derart erfolgt, daß die Hohlform Rotor eines Elektro-Motors ist.A device for carrying out the method according to the invention with a hollow mold drivable as a centrifuge, on the inner wall of which substances introduced into the hollow mold can be separated by centrifugal forces, is characterized according to the invention in that the hollow mold can be closed by two aperture diaphragms arranged perpendicular to the longitudinal axis of the hollow mold, through the openings of which at least one tube each can be displaced as a metering device along the longitudinal axis of the hollow mold, such that part of the tube (s) remains outside the hollow mold and from there can be loaded with substances to be introduced into the interior of the hollow mold and the other, in the interior located part of the tube (s) is provided with at least one outlet opening (nozzle) through which substances in the tubes first enter the interior of the hollow mold and can be deposited on the inner wall thereof, the hollow mold according to advantageous developments of the invention an R ear is closed at the end with the aperture diaphragm, the centrifugal drive of the hollow mold is carried out with the aid of a motor, with the axis of which the hollow mold is connected, or the centrifugal drive of the hollow mold is carried out in such a way that the hollow mold is the rotor of an electric motor.

Ausführungsbeispiele der Erfindung werden im folgenden anhand der Zeichnung näher beschrieben und in ihrer Wirkungsweise erläutert.Embodiments of the invention are described in more detail below with reference to the drawing and their operation is explained.

Die Figur zeigt eine schematische Darstellung einer Zentrifugenanordnung mit einer Hohlform zur Herstell von rohrförmigen Körpern nach der Erfindung.The figure shows a schematic representation of a centrifuge arrangement with a hollow mold for the production of tubular bodies according to the invention.

In ein horizontal (oder auch vertikal) gelagertes Rohr als Hohlform 1, dessen Stirnflächen durch abnehmbare und in der Größe ihrer Öffnung 5 einstellbare Aperturblenden 3 teilweise verschlossen sind, wird zunächst eine flüssige Phase 17 eingebracht und durch Zentrifugieren gleichmäßig in Form eines Flüssigkeitsfilmes 13 auf der Innenwandung 11 des als Hohlform 1 eingesetzten Rohres verteilt. Anschließend wird über eine in axialer und radialer Richtung bewegliche Dosiervorrichtung in Form von mindestens einem Rohr 7 mit Austrittsöffnungen 9 pulverförmiges Ausgangsmaterial 15 dem Innenraum des als Hohlform 1 wirkenden Rohres zugeführt. Durch Zentrifugalkräfte werden die Feststoffpartikel auf den Flüssigkeitsfilm 13 getrieben, wo eine Benetzung erfolgen kann und die feinen Teilchen mit Dispergiermittel überzogen und vor einer frühzeitigen Koagulation bewahrt werden. Im Flüssigkeitsfilm 13 driften die Feststoffpartikel nun getrennt voneinander in Richtung auf die Innenwandung 11 der Hohlform 1, wo sie mit großer Packungsdichte (50 bis 90 % der theoretisch möglichen Packungsdichte) abgelagert werden.In a horizontally (or also vertically) mounted tube as a hollow mold 1, the end faces of which are partially closed by removable and adjustable in size 5 aperture diaphragms 3, a liquid phase 17 is first introduced and by centrifugation evenly in the form of a liquid film 13 on the Distributed inner wall 11 of the tube used as a hollow mold 1. Subsequently, a metering device movable in the axial and radial direction in the form of at least one tube 7 with outlet openings 9 feeds powdery starting material 15 to the interior of the tube acting as a hollow mold 1. The solid particles are driven onto the liquid film 13 by centrifugal forces, where wetting can take place and the fine particles are coated with dispersant and are prevented from premature coagulation. In the liquid film 13, the solid particles drift separately from one another in the direction of the inner wall 11 of the hollow mold 1, where they are deposited with a high packing density (50 to 90% of the theoretically possible packing density).

Die Zwischenräume bleiben mit der flüssigen Phase, die ein z. B. Dispergiermittel und ein Bindemittel enthält, ausgefüllt. Um eine gleichmäßige Ablagerung der Feststoffpartikel längs der Rohrachse der Hohlform 1 zu erleichtern, kann die Feststoffpartikeleingabe kontinuierlich in axialer Richtung verschoben vorgenommen werden. Um eine möglichst schnelle Abscheidung zu erreichen, kann die Zugabe der flüssigen Phase 17 ebenfalls kontinuierlich über eine getrennte Dosiervorrichtung in Form eines weiteren Rohres 7' über eine Düse 99 vorgenommen und gerade so bemessen werden, daß die abgeschiedene Feststoffpartikelschicht stets nur mit einem dünnen Flüssigkeitsfilm bedeckt ist. Hierbei ergeben sich folgende Vorteile: Die Prozeßdauer kann gegenüber einer einmaligen Zugabe der benötigten flüssigen Phase erheblich vermindert werden, da die Abscheidungszeit proportional zur Viskosität der Flüssigkeit und der Filmdicke ist. Eine Separation von Feststoffpartikeln unterschiedlicher Dichte und Abmessungen wird durch diese Maßnahme minimiert. Die innen zu beschichtende Hohlform kann sowohl in horizontaler als auch vertikaler Position um ihre Längsachse gedreht werden.The gaps remain with the liquid phase, the z. B. contains dispersant and a binder. In order to facilitate a uniform deposition of the solid particles along the tube axis of the hollow mold 1, the solid particle input can be continuously shifted in the axial direction. In order to achieve the fastest possible separation, the addition of the liquid phase 17 can also be carried out continuously via a separate metering device in the form of a further tube 7 'via a nozzle 99 and can be dimensioned such that the deposited solid particle layer is always covered only with a thin film of liquid is. This has the following advantages: The process time can be considerably reduced compared to a single addition of the required liquid phase, since the deposition time is proportional to the viscosity of the liquid and the film thickness. A separation of solid particles of different densities and ab This measure minimizes measurements. The hollow mold to be coated on the inside can be rotated about its longitudinal axis in both horizontal and vertical positions.

Im folgenden werden unterschiedliche Ausführungsbeispiele zur Herstellung von Si02-Rohren hoher Dichte, Homogenität und Reinheit beschrieben.Different exemplary embodiments for the production of SiO 2 tubes of high density, homogeneity and purity are described below.

Beispiel 1:Example 1:

In ein rotierendes hochfestes Metallrohr, z. B. aus Stahl oder Aluminium, mit einer Gesamtlänge von 160 mm und einem äußeren Durchmesser von 60 mm, dessen Endflächen mit abnehmbaren Aperturblenden in einer Dicke von 5 mm versehen sind, werden bei einer Rotationsfrequenz von zunächst 1000 U/min etwa 120 ml einer 15 %-igen Polyvinylalkohollösung (Polymerisationsgrad 350) eingebracht. Nach erfolgter Gleichverteilung der Flüssigkeit über die Innenwandung des Rohres wird über eine in axialer Richtung bewegliche Dosiervorrichtung 210 g feinverteiltes hochdisperses Si02-Pulver mit einer Dosierrate von 1 g/min ebenfalls gleichmäßig durch Hin- und Herfahren der Dosiervorrichtung mit einer Geschwindigkeit von 5 m/min bei gleichzeitiger Erhöhung der Rotationsfrequenz des Rohres auf 30 000 U/min verteilt. Nach erfolgter Sedimentation der Feststoffpartikel unter einer Zentrifugalbeschleunigung, die in diesem Fall etwa 20 000 mal größer als die Erdbeschleunigung ist, wird der über der Abscheidung liegende überschüssige Flüssigkeitsfilm abgesaugt und der abgeschiedene Grünkörper durch leichte Erwärmung des Substratrohres, etwa auf 50 bis 100°C, entformt. Um die Entformung zu erleichtern, empfiehlt sich eine dünnlagige Abscheidung eines Gleitfilmes zu Beginn des Prozesses auf der Innenwandung des Rohres, z. B. aus Paraffin. Der auf diese Weise erhaltene Grönkörper zeichnet sich durch große geometrische Genauigkeit und eine nahezu ortsunabhängige Dichte aus. Letzteres und die Tatsache, daß nach Trocknung bei 120°C und Austreiben des Bindemittels durch langsames Aufheizen auf 500°C bei einer Aufheizgeschwindigkeit von 150° C/h eine geringe offene Porenstruktur zur Verfügung steht, macht eine nachfolgende chlorierende Reinigung des Grönkörpers und die Sinterung zu Quarzglasrohren möglich.Verunreinigungen können z. B. H20 oder störende Metallverbindungen sein. Derartige Verunreinigungen wurden bei 800°C in einem bei Raumtemperatur mit SOCI2 gesättigten 02-Strom einer Strömungsgeschwindigkeit von 1 bis 2 I/min beseitigt. Die Verunreinigungen werden dabei chloriert und entweichen als flüchtige Phase. Die Dichtsinterung des geringfügig offenporigen Grünkörpers zu transparentem, blasenfreiem Glas erfolgte bei 1500° C mit einer Absenkgeschwindigkeit von 3 mm/min unter einer Helium/Chlor (1 bis 3 %)-Atmosphäre eines Druckes von 105 Pa und einer Strömungsgeschwindigkeit von 1 1/min. Nach diesem Verfahren wurde ein hochreines, transparentes Quarzglasrohr hoher Oberflächengöte erhalten.In a rotating high-strength metal tube, e.g. B. made of steel or aluminum, with a total length of 160 mm and an outer diameter of 60 mm, the end faces of which are provided with removable aperture diaphragms in a thickness of 5 mm, at a rotation frequency of initially 1000 rpm, about 120 ml of a 15th % polyvinyl alcohol solution (degree of polymerization 350) introduced. After the liquid has been uniformly distributed over the inner wall of the tube, 210 g of finely divided, highly disperse SiO 2 powder with a metering rate of 1 g / min is also uniformly moved by moving the metering device back and forth at a speed of 5 m / using a metering device which is movable in the axial direction. min while increasing the rotation frequency of the pipe to 30,000 rpm. After sedimentation of the solid particles under centrifugal acceleration, which in this case is about 20,000 times greater than the acceleration due to gravity, the excess liquid film lying above the separator is suctioned off and the separated green body by slightly heating the substrate tube, for example to 50 to 100 ° C. demolded. In order to facilitate the demoulding, a thin layer deposition of a sliding film is recommended at the beginning of the process on the inner wall of the pipe, e.g. B. from paraffin. The green body obtained in this way is characterized by great geometric accuracy and an almost location-independent density. The latter and the fact that after drying at 120 ° C and expulsion of the binder by slow heating to 500 ° C at a heating rate of 150 ° C / h, a small open pore structure is available, a subsequent chlorine cleaning of the green body and sintering possible with quartz glass tubes. B. H 2 0 or interfering metal compounds. Such impurities were removed at 800 ° C in a saturated at room temperature with SOCI 2 0 2 flow at a flow rate of 1 to 2 I / min. The impurities are chlorinated and escape as a volatile phase. The sintering of the slightly open-pore green body to transparent, bubble-free glass was carried out at 1500 ° C with a lowering speed of 3 mm / min under a helium / chlorine (1 to 3%) atmosphere of a pressure of 10 5 Pa and a flow rate of 1 1 / min. A high-purity, transparent quartz glass tube with a high surface area was obtained by this process.

Beispiel 2:Example 2:

Eine beschleunigte Herstellung von Grünkörpern auf der Basis von Si02/Bindemittel kann auf die Weise erreicht werden, daß die flüssige Phase (vergleiche Beispiel 1) während der Feststoffpartikelzugabe ebenfalls kontinuierlich zugeführt wird, derart, daß nur ein dünner Flüssigkeitsfilm (1 mm, vorzugsweise 10 bis 100 µm) über den bereits abgeschiedenen Feststoffpartikeln steht. Durch diese Maßnahme ist es einerseits möglich, die Geschwindigkeit der Feststoffpartikelzugabe auf 5 g/min problemlos zu steigern und darüberhinaus eine Entmischung von Feststoffpartikelteilchen unterschiedlicher Größe während der kurzen Sedimentationszeit zu vermindern.An accelerated production of green bodies based on SiO 2 / binder can be achieved in such a way that the liquid phase (see Example 1) is also continuously fed during the addition of solid particles, such that only a thin film of liquid (1 mm, preferably 10 up to 100 µm) above the already separated solid particles. This measure makes it possible, on the one hand, to increase the speed of adding solid particles to 5 g / min without problems and, furthermore, to reduce segregation of different sizes of solid particles during the short sedimentation time.

Beispiel 3:Example 3:

Die Herstellung von Grünkörpern auf Basis von Feststoffpartikeln/Bindemittel mit Variation der Zusammensetzung über die Wanddicke kann wie folgt erfolgen:The production of green bodies based on solid particles / binders with variation of the composition over the wall thickness can take place as follows:

Zunächst wird flüssige Phase, wie in Beispiel 1 beschrieben, in die Hohlform eingebracht. Durch Zuführung unterschiedlich zusammengesetzter Ausgangspulver (Feststoffpartikel) und Variation ihres Verhältnisses zueinander über die Zeit lassen sich nahezu beliebige Zusammensetzungen über die Wanddicke aufbauen. Für die Herstellung von optischen Wellenleitern ist die definierte Änderung des Brechungsindex über den Radius von großer Bedeutung. Durch Einführung z. B. einer zweiten Dosiervorrichtung in Form eines zweiten Rohres, das sich ebenfalls in axialer Richtung verschieben läßt, kann z. B. 15 Gew.-% Ge02 enthaltendes Si02-Pulver in das Innere der rotierenden Hohlform simultan mit reinem Si02-Pulver eingebracht werden. Zu Beginn des Prozesses wird zunächst nur reines Si02-Pulver in einer Dosierrate von 1 g/min zugeführt. Während des Prozesses wird dann bei Konstanthaltung der Dosierrate von 1 g/min die Dosierung des reinen Si02-Pulvers linear bis auf Null zurückgenommen bei gleichzeitiger und entsprechender Erhöhung der Dosierrate des Si02-Ge02-Pulver-Stromes. Nach den notwendigen Zwischenschritten des Ausheizens, Reinigens, Sinterns, Kollabierens und Faserziehens lassen sich auf diese Weise GradientenIndex- Fasern mit Dämpfungen von weniger als 1 dB/km bei 1300 nm herstellen.First, liquid phase, as described in Example 1, is introduced into the mold. By supplying differently composed starting powder (solid particles) and varying their relationship to each other over time, almost any composition can be built up over the wall thickness. The defined change in the refractive index over the radius is of great importance for the production of optical waveguides. By introducing z. B. a second metering device in the form of a second tube, which can also be moved in the axial direction, z. B. 15 wt .-% Ge0 2 containing Si0 2 powder can be introduced into the interior of the rotating hollow mold simultaneously with pure Si0 2 powder. At the beginning of the process, only pure SiO 2 powder is fed in at a dosage rate of 1 g / min. During the process, the metering rate of the pure Si0 2 powder is then linearly reduced to zero while the metering rate is kept constant at 1 g / min, with a simultaneous and corresponding increase in the metering rate of the Si0 2 -Ge0 2 powder stream. After the necessary intermediate steps of baking, cleaning, sintering, collapsing and fiber drawing, gradient index fibers with attenuation of less than 1 dB / km at 1300 nm can be produced in this way.

Beispiel 4:Example 4:

Die Herstellung von rohrförmigen Körpern auf Feststoffpartikelbasis, bei dem das feinpulverige Ausgangsmaterial in eine hydrophobe Flüssigkeit zentrifugiert wird, kann auf folgende Weise vorgenommen werden.The production of tubular bodies based on solid particles, in which the finely powdered starting material is centrifuged into a hydrophobic liquid, can be carried out in the following way.

Es wird gearbeitet wie unter den Beispielen 1 bis 3 beschrieben, mit dem Unterschied, daß anstelle von wässerigen Polyvinylalkohollösungen ein bei Raumtemperatur flüssiges Paraffin verwendet wird.The procedure is as described in Examples 1 to 3, with the difference that instead of aqueous polyvinyl alcohol solutions, a paraffin liquid which is liquid at room temperature is used.

Nach Sedimentation des Grünkörpers kann die Entformung aus der Hohlform durch eine Erwärmung der Hohlform auf etwa 100 bis 150°C vorgenommen werden.After sedimentation of the green body, demolding from the hollow mold can be carried out by heating the hollow mold to about 100 to 150 ° C.

Statt einer hydrophoben Flüssigkeit als Bindemittel lassen sich auch mit Vorteil thermoplastische oder duroplastische Kunststoffe als Dispergiermatrix und Bindemittel einsetzen. Als interessant hat sich die Verwendung von solchen UV-härtenden Lacken herausgestellt, die bei Raumtemperatur dünnflüssig sind und erst durch Einwirkung von UV-Strahlung aushärten.Instead of a hydrophobic liquid as the binder, it is also advantageous to use thermoplastic or thermosetting plastics as the dispersion matrix and binder. It has proven to be interesting to use UV-curing lacquers which are thin at room temperature and only harden when exposed to UV radiation.

Beispiel 5:Example 5:

Die Herstellung und Abscheidung von Feststoffpartikeln in einem einzigen Prozeßschritt mit anschließendem Zentrifugieren kann wie folgt vorgenommen werden:

  • Zunächst wird flüssige Phase, wie in Beispiel 1 beschrieben, in die Hohlform eingebracht.
The production and separation of solid particles in a single process step with subsequent centrifugation can be carried out as follows:
  • First, liquid phase, as described in Example 1, is introduced into the mold.

Als Ausgangsmaterialien för die Erzeugung der festen Phase dienen gasförmige Substanzen wie SH4 und 02, die über einen in axialer Richtung verschiebbaren Ringbrenner in den Innenraum der rotierenden Hohlform unter gleichzeitiger reaktiver Umsetzung eingebracht werden. Wegen der entstehenden und abzuföhrenden Gase werden die Reaktionen in Brennerdüsen durchgeföhrt, die zylindersymmetrisch auf einem Ring mit dem Radius ro<r<r; (ro = Achse der rotierenden zylindrischen Hohlform; ri = Innenradius der zylindrischen Hohlform) liegen. Die Folge ist, daß die unmittelbar hinter den Brennerdösen entstehenden Feststoffpartikel direkt in das Beschleunigungsfeld der Zentrifuge geraten und in Richtung auf die Innenwandung der Hohlform sedimentieren. Ein Vorteil dieses in situ-Prozesses ist die genaue Dosierbarkeit der Materialien und ihre nahezu ideale Dispersion in der Gasphase.The starting materials for the generation of the solid phase are gaseous substances such as SH 4 and O 2 , which are introduced into the interior of the rotating hollow mold via a ring burner which can be displaced in the axial direction, with simultaneous reactive conversion. Because of the gases that are created and to be removed, the reactions are carried out in burner nozzles, which are cylindrically symmetrical on a ring with the radius r o <r <r; (r o = axis of the rotating cylindrical hollow form; r i = inner radius of the cylindrical hollow form). The result is that the solid particles formed immediately behind the burner nozzles get directly into the acceleration field of the centrifuge and sediment in the direction of the inner wall of the hollow mold. An advantage of this in situ process is the precise meterability of the materials and their almost ideal dispersion in the gas phase.

Es wurde mit folgenden Prozeßparametern gearbeitet:

  • Gasflüsse: SiH4=165 cm3/min; 02=650 cm3 /min; diese Werte beziehen sich auf einen Druck von 10,11.104 Pa;
The following process parameters were used:
  • Gas flows: SiH 4 = 165 cm 3 / min; 0 2 = 650 cm 3 / min; these values refer to a pressure of 10.11.10 4 Pa;

Umdrehungsgeschwindigkeit der Hohlform: 1500 U/min;

  • Abscheidungsdauer: 6 Stunden;
  • Abgeschiedene Si02-Feststoffpartikelmasse: 180 g
Speed of rotation of the mold: 1500 rpm;
  • Deposition time: 6 hours;
  • Deposited Si0 2 solid particle mass: 180 g

Als Ausführungsbeispiele wurden Beispiele beschrieben, die sich auf die Herstellung von hochreinen oder dotierten Quarzglasrohren beziehen. Nach dem vorliegenden Verfahren und der vorliegenden Vorrichtung lassen sich jedoch auch Rohre aus beliebigen anderen Werkstoffen herstellen, z. B. aus Aluminiumoxid oder Eisen.Examples have been described as exemplary embodiments which relate to the production of high-purity or doped quartz glass tubes. According to the present method and the present device, however, pipes can also be produced from any other materials, e.g. B. made of aluminum oxide or iron.

Hochreine und maßgenaue Quarzrohre, wie sie nach dem vorliegenden Verfahren herstellbar sind, können bei der Herstellung von optischen Wellenleitern, aber auch bei der Herstellung von Halogen- und Gasentladungslampen Anwendung finden.Highly pure and dimensionally accurate quartz tubes, as can be produced by the present method, can be used in the production of optical waveguides, but also in the production of halogen and gas discharge lamps.

Claims (29)

1. A method of manufacturing tubes, in which a mixture of the tube material in powder form (solid phase (15) and a binder in a liquid phase (17) is introduced into a tubular mould (1) having a geometry which corresponds to the geometry of the tube to be formed, in such manner that the tubular mould is rotated about its longitudinal axis, the powder-binder mixture depositing on the inner wall (11) of the tubular mould and excessive binder being removed after which the green body formed is processed further, characterized in that the solid phase (15) and the liquid phase (17) are introduced separately into the tubular mould (1).
2. A method as claimed in claim 1, characterized in that the binder and the solid phase (15) are introduced into the tubular mould (1) after each other via dosing devices (7, 7'), in which first the liquid phase (17) is deposited on the inner wall (11) of the tubular mould (1).
3. A method as claimed in claim 2, characterized in that the binder and the solid phase (15) are introduced into the tubular mould (1) after each other and several times in succession via the dosing devices (7, 7').
4. A method as claimed in claim 1, characterized in that the binder and the solid phase (15) are simultaneously introduced into the tubular mould (1) via separate dosing devices (7, 7'), excessive liquid phase (17) being sucked off during the process.
5. A method as claimed in claims 1 to 4, characterized in that the dosing devices (7, 7') and the tubular mould (1) are moved relatively to each other during the introduction of the solid phase (15) and the liquid phase (17).
6. A method as claimed in claim 1, characterized in that a lubricating film for a better remowal of the green body from the mould is provided on the inner wall (11) of the tubular mould (1) prior to introducing the liquid phase (17) and the solid phase (15).
7. A method as claimed in claim 6, characterized in that high-molecular hydrocarbons are provided as the lubricating film.
8. A method as claimed in claim 1, characterized in that the binder is multiphase.
9. A method as claimed in claim 1, characterized in that a hydrophobic fluid is used as the binder.
10. A method as claimed in claim 9, characterized in that a paraffin which is liquid at room temperature is used as the binder.
11. A method as claimed in claim 1, characterized in that the solid phase (15) is a powder-ceramic material.
12. A method as claimed in claim 11, characterized in that the powder-ceramic material is a material suitable for the manufacture of optical waveguides.
13. A method as claimed in claim 11, characterized in that the powder-ceramic material is A1203.
14. A method as claimed in claim 12, characterized in that the material is highly-dispersed Si02- powder of a grain size in the range from 5 to 500 nm, preferably from 10 to 200 nm, without or with a doping suitable for the adjustment of a desirable refractive index.
15. A method as claimed in any of the preceding claims 1 to 14, characterized in that the solid phase (15) is manufactured via a chemical process in the gaseous phase.
16. A method as claimed in claim 15, characterized in that the manufacture of the solid phase (15) is carried out via a chemical process in the gaseous phase immediately prior to its deposition on the inner wall (11) of the tubular mould (1
17. A method as claimed in claim 16, characterized in that SiH4 and 02 are used as gaseous starting substances.
18. A method as claimed in claim 16, characterized in that the heating of the gaseous starting substances is carried out via at least one heat- ingdevice which is axially mowable over the tubular mould (1).
19. A method as claimed in claim 1, characterized in that the solid phase (15) is a powder- metallurgic material.
20. A method as claimed in claim 1, characterized in that the solid phase (15) is introduced into the tubular mould (1) in successive batches of different chemical composition.
21. A method as claimed in claim 20, characterized in that the solid phase (15) is introduced into the tubular mould (1) in such manner that layers of different composition corresponding to a desired refractive index profile deposit on the inner wall (11) of the tubular mould.
22. A method as claimed in claim 14, characterized in that Ge02 is used as a dopant.
23. A device for carrying out the method as claimed in claims 1 to 22, comprising a tubular mould (1) which can be driven as a centrifuge, on the inner wall (11) of which substances introduced into the mould can be deposited by centrifugal forces, is characterized in that the tubular mould (1) can be closed by two diaphragms (3) provided at right angles to the longitudinal axis of the tubular mould and through the apertures (5) of which at least one tube (7, 7') can be moved as a dosing device along the longitudinal axis of the tubular mould, in such manner that a part of the tube(s) remai n(s) outside the tubular mould from where it can be provided with materials to be introduced into the inner space of the tubular mould and the other part of the tube(s) present in the inner space of the tubular mould comprises at least one outlet aperture (nozzle) (9, 99) through which materials present in the tubes first reach the inner space of the tubular mould and can be deposited on the inner wall (11) of the tubular mould.
24. A device as claimed in claim 23, characterized in that the tubes (7, 7') are rotatable about their longitudinal axes.
25. A device as claimed in claim 23, characterized in that the tubular mould (1) is a tube which can be closed at its end faces by diaphragms (3).
26. A device as claimed in claim 23, characterized in that the centrifugal drive of the tubular mould (1) takes place by means of a motor to the shaft of which the tubular mould is connected.
27. A device as claimed in claim 23, characterized in that the centrifugal drive of the tubular mould (1) occurs in such manner that the tubular mould is the rotor of an electric motor.
28. The use of the green body manufactured according to the method as claimed in claims 1 to 22 as a preform of high density and homogeneity for optical waveguides.
29. The use of the green body manufactured according to the method as claimed in the claims 1 to 22 as a preform for envelopes for halogen or gas discharge lamps.
EP85200214A 1984-02-21 1985-02-20 Process for producing tubular bodies and device for carrying out the process Expired EP0153785B1 (en)

Applications Claiming Priority (2)

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DE19843406148 DE3406148A1 (en) 1984-02-21 1984-02-21 METHOD FOR THE PRODUCTION OF TUBULAR BODIES AND DEVICE FOR IMPLEMENTING THE METHOD
DE3406148 1984-02-21

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EP0153785A2 EP0153785A2 (en) 1985-09-04
EP0153785A3 EP0153785A3 (en) 1987-05-27
EP0153785B1 true EP0153785B1 (en) 1989-07-12

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EP (1) EP0153785B1 (en)
JP (1) JPS60215533A (en)
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US7666517B2 (en) 2001-06-27 2010-02-23 Cyclics Corporation Isolation, formulation, and shaping of macrocyclic oligoesters
US7750109B2 (en) 2000-09-01 2010-07-06 Cyclics Corporation Use of a residual oligomer recyclate in the production of macrocyclic polyester oligomer
US7767781B2 (en) 2000-09-01 2010-08-03 Cyclics Corporation Preparation of low-acid polyalkylene terephthalate and preparation of macrocyclic polyester oligomer therefrom

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US7767781B2 (en) 2000-09-01 2010-08-03 Cyclics Corporation Preparation of low-acid polyalkylene terephthalate and preparation of macrocyclic polyester oligomer therefrom
US8283437B2 (en) 2000-09-01 2012-10-09 Cyclics Corporation Preparation of low-acid polyalkylene terephthalate and preparation of macrocyclic polyester oligomer therefrom
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US7666517B2 (en) 2001-06-27 2010-02-23 Cyclics Corporation Isolation, formulation, and shaping of macrocyclic oligoesters

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CA1247321A (en) 1988-12-28
DE3406148C2 (en) 1987-09-03
JPS60215533A (en) 1985-10-28
EP0153785A3 (en) 1987-05-27
JPH0475172B2 (en) 1992-11-30
US5182052A (en) 1993-01-26
EP0153785A2 (en) 1985-09-04
DE3571429D1 (en) 1989-08-17

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